According to the relevant provisions of IMO and China MSA, most ships are installed communication rescue equipment such as VHF radio station, marine radio telephone, GPS and INMARSAT SES. Ships can call rescue teams for help through these equipments in case of accident. However, when someone has fallen into water, he or she will drift away from the site under the action of current. As the drowning person mostly carries no personal communication or position indicating equipment, it is very difficult for rescuers to determine the detailed position of the drowning person, when they arrive to find the wrecked ship. Up to now, rescuers fall behind in rescue methods. They can only speculate the possible location of the drifted drowning person through analysis of water flow condition within the accidental area, or dragnet over sea with camera system, illuminating system and infrared night-vision system. Anyway, it is even tough to speculate the location of drowning person at coastal reefs with complex and ever-changing circulation. Rescue becomes more difficult during severe weather.